* Bump API patch number and header version number to 43 for this update.
Github Issues:
* Make clearer that color write mask is applied regardless of whether
blending is enabled, by referring to the
<<framebuffer-color-write-mask,Color Write Mask>> section (public issue
241).
* Fix public issue 414:
** Added two new command buffer states (invalid, pending), and an explicit
"command buffer lifecycle" section to explain them.
** Replaced "pending execution" with "in the pending state".
** Replaced a bunch of "this will invalidate the command buffer" language
with "this will move the command buffer to the invalid state", and added
validation language for what state those command buffers should be in.
** Added additional validation language about what state a command buffer
should be in for various commands that affect it.
** Added invalidation language to destroy commands in the lifetimes section
of fundamentals.
** Added command buffers to list of objects which must not be deleted
whilst a (primary) command buffer is in the recording or pending state.
* Update `GL_KHR_vulkan_glsl` extension to allow anonymous push constant
blocks (public issue 428).
Internal Issues:
* Document rules about extension interactions in the style guide (internal
issue 579).
* Require ename:VK_PRESENT_MODE_MAILBOX_KHR support in queries of surfaces
created with flink:vkCreateWaylandSurfaceKHR using the
VK_KHR_wayland_surface extension (internal issue 666).
* Remove Valid Usage constraints for flink:vkAllocateDescriptorSets when
the `VK_KHR_maintainance1` extension is present (internal issue 686).
* Remove undocumented KHX-variants of vkGetPhysicalDeviceProperties2KHR
and vkGetPhysicalDeviceImageFormatProperties2KHR from the
<<VK_KHX_external_memory_capabilities>> and
<<VK_KHX_external_semaphore_capabilities>> extensions.
New Extensions:
* `VK_EXT_hdr_metadata`
* `VK_GOOGLE_display_timing`
Jon Leech